Sump Pump Systems Revisited

I recently came across a sump pump installation during a home inspection that caught me by surprise–and that takes some doing. Below is a picture of the pit. So, what was wrong with this sump pump pit installation in the following photo:

A sump pump pit in a home that I was inspecting. What is wrong with this installation?

Hopefully, your answer is that the pit was constructed of cardboard. More accurately, the pit was constructed using a concrete form tube, such as Sonoco’s Sonotube brand (http://www.sonotube.com/sonotube.html) or Quikrete’s Quik-Tube brand (http://www.quikrete.com/productlines/QuikTubeBuildingForm.asp). For those unfamiliar with form tubes, they are thick-walled, multi-layered cardboard tubes that are used for rapidly constructing concrete forms primarily for column piers or foundations. They have been a boon for structural construction in that, when a pier is needed, say to support a deck column, the installer only needs to dig a hole large enough for the form tube, (hopefully) install a footing or compacted base material, place the tube in the hole with rebar if needed, and pour concrete into the tube. (I have also heard that form tubes make a wicked impromptu drum.)

For the installation in the photo, the form tube was used as a sump pump pit. It appeared to have been installed a number of years after the home was built. The basement in which the pit was installed had apparent moisture intrusion issues, which I concluded were partially due to the water drainage for several adjacent properties being run within 20 feet of the basement. The installation indicated that a hole had been made in the basement’s concrete floor and the sub-slab soil removed to a couple of feet. Then, gravel appeared to have been put in the bottom of the hole and the form tube installed and concreted in place. As the photo shows, a drain line is run through the side of the form tube, although from where it came could not be determined.

So what is wrong with using a cardboard tube for the pit. The darker tube area deeper in the pit is the clue. This part of the tube is saturated with moisture, even though a number of weeks had passed since the area received measurable rain. I was able to stick a screwdriver blade through the darkened area of the tube, verifying that it was wet and degrading. Over time, the cardboard will likely completely degrade. As that happens, soil around the pit will erode into the pit decreasing the pit’s depth. Erosion of the soil will also create a void under the slab and quite possibly under the nearby foundation. And then, the home has great risk of structural issues that will be expensive to fix.

But, degradation of the pit and potential structural issues are not the only problems. Water flowing into the pit is also likely not contained within the pit. Instead, it is flowing out of the pit into the soil under the basement slab. The lower part of the tube still being wet despite no rain for awhile shows that the soil at that level is also wet, which was verified by the mud on the screwdriver blade when I withdrew it. Water in the soil below the slab will wick throughout the soil up to the slab. If an adequate vapor barrier was not installed below the slab, water vapor from the soil can flow through the slab and into the home, causing moisture issues inside the home. Even if the sump pump removes the loose water under the slab, as the cardboard shows, the soil will still hold water because that is what soil does. This moisture will eventually evaporate to water vapor, which could flow into the home through the slab if an adequate vapor barrier is not present.

And what happens if a LOT of water is flowing into the sump pit through the drain line in the photo? In this home, cracks in the slab had been sealed, which may have been precautionary. On the other hand, water could have percolated up through the slab already. A large volume of water flowing into the sump pit and under the slab could lead to water flowing up through cracks in the slab, even if a vapor barrier were present. Water could flow out of cracks in the slab without coming out of the sump–water seeks its own level and the top of the slab around the cracks could be lower than the top of the slab around the sump pit. If this drain line is carrying water from around the exterior of the basement foundation, there could be a LOT of water, especially if water from nearby properties is being channeled near that basement wall.

Water flowing into the sump pit will also be carrying small soil particles. Although soil particles being present in groundwater is normal, if that water is flowing from an area prone to soil erosion, the amount of soil particles could be greater than normal. These soil particles are sucked into the sump pump with the water. In turn, these soil particles erode the pump’s impeller, the part of the pump that moves the water . Erosion of a pump’s impeller shortens the pump’s life, meaning that the pump would need replacing more often than normal. (Note that for most pumps, replacement is cheaper than trying to rebuild them.) Erosion of other materials inside the pump likely also occurs, decreasing the pump’s efficiency. That is, the same amount of electricity is being used to run the pump; but the pump is not moving as much water for the amount of electricity used. You pay the same amount for the electricity, but get less for it. BTW, if you have not priced a sump pump lately, they start at about $125 just for the pump–plumbers, if needed, are much more expensive.

For the sump pump system in the photo, it will need replacing. Hopefully, a proper durable sump pit and pump will be used. I also hope that the person who installed this sump pump system is not the one hired for the replacement job. The homeowner assured me that person will NOT be the one they hire. I just hope that no one else has hired him/her for their plumbing work. Sump pump systems seem like such simple things, and they are to an extent. However, they are very important systems for keeping a home high and dry. They should be given the priority they deserve.